----- Original Message -----
From: Tony Nixon

> Kieran Miller wrote:
> >
> > Hi,
> >
> > I have a PIC 16F874 sitting in a socket on my PCB, and as far as I am
> > aware, it's simply refusing to start up.
>
>
> Check that MCLR is connected to VCC
>

>From what I can tell on the F84 (I'm not familiar with the 874), the
crystal fires up whether MCLR is at 0V or Vcc. Surprised me. The only
comment I'd have otherwise about MCLR is that I got caught out badly
once (and only once !!) by a very very fine solder whisker between 0V
and MCLR, which on the F84 are adjacent pins.

SLEEP stops the oscillator -- have you got a SLEEP routine ?